Submarine drone dives into hunt for missing MH370 jet

Time to drop the drone. The team looking for the missing Malaysia Airlines jet in the Indian Ocean is to deploy an autonomous submarine for the first time. The Bluefin-21 underwater vehicle will use sonar beams to create high resolution 3D images of the seabed some 4500 metres down.

The sub is being dispatched on a series of 24-hour, 40-square-kilometre autonomous search missions by the Australian military ship Ocean Shield because the multinational search's Joint Agency Coordination Centre (JACC) in Perth, Australia, believes the batteries on the two flight recorder "pingers" of flight MH370 are now exhausted.

As a result, the searchers can no longer listen out for further pings to narrow down where the wreckage might be. Instead, they will have to rely on the four pings heard to date to work out where the submarine should begin its seabed survey.

Angus Houston, head of the JACC, says there may be one more clue to helping pick the right area for the Bluefin-21 to explore: an oil slick detected on 13 April some 5500 metres downwind and "down-sea" of the area where the pings were sensed may help narrow down the search area – if chemical analysis of a 2-litre sample shows that the oil came from a plane.

The Bluefin-21 projects a sonar beam 500 metres either side of it as it moves, gradually building up an image of the seabed. The sub is designed for missions at depths of 4500 metres – which is thought to be the depth the MH370 wreckage would lie in. "But we have designed, built and operated a 6000-metre depth version as part of a DARPA programme," says David Kelly, president of its maker Bluefin Robotics in Quincy, Massachusetts.

The Bluefin-21 sub is untethered so doesn't need to drag a heavy 4500-metre-long power cable behind it. It simply "executes a planned mission without operator intervention", says Kelly.

One downside of this is that the submarine, which moves at about walking pace, does not send back any live sonar images. It will have to surface after 20 hours in the water to have its data downloaded and analysed and its batteries replaced.

Houston cautions that they may still not find anything on the unpredictable, unexplored seabed. "This is an area that is new to man," he warns.

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The Bluefin-21 sub will scan the depths where flight MH370 is thought to have fallen (Image: Getty Images)